An actual “linear” amplifier, such as an RF amplifier, produces some distortion, such as generating second and third harmonics of the fundamental frequency, generating frequency-mixed signals, and generating intermodulation products. For example, a “linear” amplifier receiving sine waves f1 and f2 will output the following signals of various magnitudes. The second and third order signals are output due to distortion:
TERMOUTPUTFREQUENCYlinearfundamentalf1, f22nd order2nd harmonic2f1, 2f23rd order3rd harmonic3f1, 3f22nd orderfrequency mixing(f2 − f1), (f2 + f1)3rd order3rd order intermod. products(2f2 − f1), (2f1 − f2)
The output current of the amplifier can be described by the following power series, limited to the third order:iout=gm1Vin+gm2Vin2+gm3Vin3,  eq. 1where the expansion coefficients gm1, gm2, gm3 are equal to:gm1(Vin)=dIout/dVin gm2(Vin)=½d2Iout/dV2in=½dgm1/dVin gm3(Vin)=⅙d3Iout/dV3=⅓dgm2/dVin 
Here, gm1Vin is the linear amplification term, gm2Vin2 corresponds to the second order and mixing products, and gm3 Vin3 represents the third order and intermodulation products.
The third order intermodulation (IM3) products are the most problematic since they may occur near a fundamental frequency and may be difficult to filter out.
In many applications where signal fidelity is the paramount goal, a Class A amplifier is the logical choice. The applicable Class A amplifier in this present disclosure is a bipolar, common emitter-connected transistor, referred to herein as a CE transistor. A Class A amplifier is always forward biased when amplifying an AC input signal. Therefore, a DC bias must be applied to the base of the CE transistor to keep it on at all expected levels of the AC signal to be amplified.
However, even when biased into Class A there are significant third order intermodulation (IM3) products produced by the inherent non-linearity of the CE transistor.
Therefore, what is desired is a technique to achieve an improved linearity of a Class A amplifier circuit by eliminating or mitigating the IM3 products.